Secondary Logo

Intravenous Infusion of Mesenchymal Stem Cells Is Associated With Improved Myocardial Function During Endotoxemia

Weil, Brent R.*; Herrmann, Jeremy L.*; Abarbanell, Aaron M.*; Manukyan, Mariuxi C.*; Poynter, Jeffrey A.*; Meldrum, Daniel R.*†‡§

doi: 10.1097/SHK.0b013e318225f6ae
Basic Science Aspects
Free

Mesenchymal stem cells (MSCs) possess immunomodulatory properties and may curtail the inflammatory response that characterizes sepsis and other systemic inflammatory states. We aimed to determine whether intravenous infusion of MSCs is associated with reduced inflammation and improved myocardial function in a rat model of endotoxemia. Adult Sprague-Dawley rats were administered saline (vehicle) or LPS (5 mg/kg) via tail vein injection. Treatments, either vehicle or 2 × 106 MSCs, were infused 1 h later via tail vein. Animals were randomly assigned to the following groups: (a) vehicle + vehicle (control; n = 6), (b) LPS + vehicle (n = 6), or (c) LPS + MSCs (n = 6). Six hours after induction of endotoxemia, left ventricular ejection fraction (EF) and fractional shortening (FS) was assessed via parasternal short-axis M-mode echocardiography. Hearts and serum were collected for determination of cytokine levels via enzyme-linked immunosorbent assay. Animals injected with LPS + vehicle exhibited depressed cardiac function as indicated by a 26% and 37% reduction in EF and FS from baseline, respectively. Treatment with MSCs was associated with improved cardiac function compared with vehicle treatment as indicated by a reduction in EF and FS of only 10% and 17%, respectively (P < 0.05). Myocardial levels of TNF-α, IL-1β, and IL-6 were elevated in LPS-treated animals versus control. Similarly, serum levels of IL-1β, IL-6, and IL-10 were increased in LPS-treated animals. Treatment with MSCs, however, was associated with significant reductions in serum levels of IL-1β and IL-6 and in myocardial levels of TNF-α, IL-1β, and IL-6. In addition, treatment with MSCs was associated with a further increase in serum IL-10. Infusion of MSCs modulates the systemic inflammatory response and is associated with improved cardiac function during endotoxemia.

Departments of *Surgery, Cellular and Integrative Physiology, and Center for Immunobiology, Indiana University School of Medicine; and §Indiana University Health Cardiovascular Surgery, Methodist Hospital, Indianapolis, Indiana

Received 13 Apr 2011; first review completed 28 Apr 2011; accepted in final form 16 May 2011

Address reprint requests to Daniel R. Meldrum, MD, 2017 Van Nuys Medical Science Bldg, 635 Barnhill Dr, Indianapolis, IN 46202. E-mail: dmeldrum@iupui.edu.

This work was supported in part by NIH R01GM070628 (to D.R.M.), NIH R01HL085595 (to D.R.M.), NIH F32HL093987 (to B.R.W.), NIH F32HL092718 (to A.M.A.), and NIH F32HL092719 (to J.L.H.).

This work was presented at the 33rd Annual Conference on Shock in Portland, Oregon, June 2010.

Back to Top | Article Outline

INTRODUCTION

Effective techniques for modulating the often maladaptive systemic inflammatory response that characterizes sepsis have long been sought. At its core, sepsis is a disorder of the immune system in which a vigorous proinflammatory response by immune cells early in the course contributes to a state of ongoing immune dysregulation and immunoparalysis. Organ injury and dysfunction are the hallmarks of severe sepsis and are responsible for the majority of the associated morbidity and mortality. Cardiac injury and dysfunction are commonly observed during the course of sepsis, can manifest as impaired systolic and diastolic function, and contribute substantially to the cardiovascular collapse and poor tissue perfusion that occur during sepsis (1-3). Proinflammatory cytokines such as TNF-α, IL-1β, and IL-6 are elaborated by macrophages and other cell types in large quantities during sepsis and directly suppress cardiac dysfunction (4-6). These cytokines have similarly detrimental effects on multiple organs and contribute to the multiorgan dysfunction syndrome observed frequently in severe sepsis. The ability to effectively prevent, reverse, and/or modulate this harmful inflammatory response and the ensuing high rates of organ failure and death would be a boon for the treatment of thousands of hospitalized patients each year.

Recently, mesenchymal stem cells (MSCs) have been observed to modulate this inflammatory response in such a way that may suggest a benefit to their use as therapeutic agents in the treatment of sepsis (7-10). Mesenchymal stem cells are a dynamic therapeutic option that may offer therapeutic benefit via a variety of mechanisms. Indeed, early observations made in the setting of laboratory models of sepsis show that MSCs can interact with cells of the immune system, modulate their function, and alter the cytokine milieu in a manner that may hold benefit for the septic host (8, 9). Systemic infusion of MSCs has been associated with reduced systemic proinflammatory cytokine levels, reduced organ injury, and improved survival in models of endotoxemia and polymicrobial sepsis (8, 9, 11-13). These characteristics of MSCs, in addition to their ease of harvest and maintenance in culture along with their immunoprivileged status-a trait that may allow for the potential use of allogeneically derived cell-make MSCs attractive candidates for the treatment of sepsis and the systemic inflammatory response syndrome (SIRS) (14). The characterization of these cells when infused in this setting, however, is in its infancy, and their ability to influence the cardiac dysfunction that is characteristic of sepsis remains unknown. We hypothesized that intravenous infusion of rat bone marrow-derived MSCs would be associated with improved in vivo cardiac function and reduced systemic and myocardial inflammation during endotoxemia.

Back to Top | Article Outline

MATERIALS AND METHODS

Animals

Male Sprague-Dawley rats (weighing 250-300 g; Harlan, Indianapolis, Ind) were fed a standard diet and acclimated in a quiet room for 2 weeks before experiments. The animal protocol was reviewed and approved by the Indiana Animal Care and Use Committee of Indiana University. All animals received humane care in compliance with the Guide for the Care and Use of Laboratory Animals (NIH publication 85-23, revised 1985).

Back to Top | Article Outline

Isolation and culture of rat bone marrow MSCs

Mesenchymal stem cells were obtained using adhesion to cell culture plastic as previously described (15). Briefly, 6- to 8-week-old male Sprague-Dawley rats were killed via pentobarbital overdose, and bone marrow stromal cells were collected from femurs and tibias by flushing the shaft with chilled complete media (Iscove's modified Dulbecco medium supplemented with 10% fetal bovine serum and 1% penicillin-streptomycin [GIBCO Invitrogen, Carlsbad, Calif]). Cells were washed with media and centrifuged for 5 min at 300 revolutions/min at 4°C. The pellet was resuspended and cultured in 75-cm2 culture flasks with complete media at 37°C, 90% humidity, and 5% CO2 in air. Mesenchymal stem cells preferentially attach to polystyrene surfaces, and after 48 h, nonadherent cells were discarded. Fresh medium was added and replaced every 3 to 4 days. After passage 3, cell surface marker expression was analyzed via flow cytometry to determine purity of the MSC population. Mesenchymal stem cells were collected for experiments between passages 4 and 7 via trypsinization and resuspended in sterile saline at a concentration of 4 × 106 cells/mL immediately before injection.

Back to Top | Article Outline

Flow cytometry and cell surface marker analysis

Flow cytometry was used to assess the cell surface marker profile of the bone marrow-isolated cell population as previously described (16). Adherent cells were lightly trypsinized, harvested, and incubated with the specific antibodies (1 μg/1 × 105 cells) for 30 min at 4°C in the dark. The following antibodies were used: anti-CD45-fluorescein isothiocyanate, anti-CD11b/c-phycoerythrin, and anti-CD90-phycoerythrin. The recommended isotype controls for each fluorochrome were used. All antibodies and isotype controls were purchased from BD Biosciences (Pharmingen, San Jose, Calif). Mesenchymal stem cells were harvested and incubated with the specific antibodies (1 μg/1 × 105 cells) for 30 min at 4°C in the dark. After incubation, the cells were washed with phosphate-buffered saline and fixed in 1% formalin overnight. Cells were analyzed the following day using a FACS Calibur cytometer (BD Biosciences).

Back to Top | Article Outline

Endotoxemia and treatment protocol

Animals (n = 18) were randomly assigned to the following groups (n = 6 per group): (a) saline + saline (control), (b) LPS + saline, and (c) LPS + MSCs. LPS derived from Salmonella typhimurium (Sigma, St Louis, Mo) was administered in 0.5 mL of saline via lateral tail vein injection at a dose of 5 mg/kg at hour 0. After 1 hour, 0.5 mL of saline or 2 × 106 cells in 0.5 mL of saline were administered via lateral tail vein injection. All animals received equal volumes of saline at each time point.

Back to Top | Article Outline

Echocardiography

In vivo left ventricular function was assessed via parasternal short-axis two-dimensional M-mode echocardiography at hour 0 (baseline) and at hour 6 for all animals. Animals were anesthetized with the minimum amount of inhaled isoflurane to prevent movement. Hair was removed from the chests by electric razor, and animals were positioned supine. Electrodes placed on the extremities were used to monitor cardiac rate and rhythm during the procedure. The probe was placed on the anterior chest, and the cardiac parasternal short axis was visualized. Left ventricular ejection fraction (EF) and fractional shortening (FS) were measured over three adjacent cardiac cycles. Measurements were repeated in triplicate, and the mean values of EF and FS are reported.

Back to Top | Article Outline

Serum and tissue collection

Animals were killed via pentobarbital overdose at hour 6 (following echocardiography). Median sternotomy was performed, and blood was collected via right ventricular puncture and centrifuged at 2,000g at 4°C for 10 min. Serum was collected and stored at −80°C until further use. Hearts were harvested, and ventricular tissue was flash frozen and stored at −80°C until further use.

Back to Top | Article Outline

Enzyme-linked immunosorbent assay

TNF-α, IL-1β, IL-6, and IL-10 levels in serum and myocardial tissue a were determined by enzyme-linked immunosorbent assay (ELISA) using commercially available kits (R&D Systems, Inc [Minneapolis, Minn] and BD Biosciences/Pharmingen). Enzyme-linked immunosorbent assay was performed according to the manufacturer's instructions. All samples and standards were measured in duplicate. In preparation for ELISA, cardiac ventricular tissue was homogenized in cold radioimmunoprecipitation assay buffer (Sigma) and then centrifuged at 12,000 revolutions/min for 10 min. Protein concentrations in extracts were determined via biophotometer, and ELISA values were normalized to these values.

Back to Top | Article Outline

Tracking of injected cells

In a separate group of animals, MSCs were treated with a fluorescent cell membrane-labeling diI compound before injection (Vybrant DiI cell-labeling solution; Invitrogen). Animals underwent the same experimental protocol after which the hearts, lungs, livers, and spleens were collected and preserved in 4% paraformaldehyde overnight. Tissues were subsequently embedded in HistoPrep medium (Thermo Fisher Scientific, Waltham, Mass) and sectioned into 5-μM sections for analysis. Sections were analyzed with the use of a Nikon TE2000U microscope (Nikon, Melville, NY) for the presence of the DiI-labeled cells at 100× magnification. Images were digitized and merged with QCapture software (QImaging, Surrey, British Columbia, Canada).

Back to Top | Article Outline

Presentation of data and statistical analysis

All reported values represent mean ± SEM. Data were compared using Student t test or, in the case of multiple comparisons, with one-way ANOVA and post hoc Tukey test. P < 0.05 was considered significant.

Back to Top | Article Outline

RESULTS

Cell surface marker expression

Cell surface marker profiles of rat bone marrow stromal cells were assessed via flow cytometry using antibodies to CD45, CD11b/c, and CD90. In previous studies, rat bone marrow-derived MSCs have been characterized as being negative for the hematopoietic stem cell and monocytic surface markers, CD45 and CD11b/c, respectively, and positive for the MSC marker, CD90. Results are plotted as histograms (Fig. 1). Analyzed cells predominately did not express CD45 or CD11b/c, but did express CD90, consistent with the previously outlined definition of rat bone marrow-derived MSCs. In total, the population of MSCs used was greater than 92% pure as determined by this surface marker expression profile.

Fig. 1

Fig. 1

Back to Top | Article Outline

In vivo cardiac function

Global left ventricular cardiac function was assessed in vivo using two-dimensional M-mode echocardiography in all animals at baseline (hour 0) and at hour 6. Baseline measurements of EF and FS revealed no differences between groups (Fig. 2A). Animals receiving LPS displayed physical signs of systemic illness including lethargy, piloerection, and diarrhea. Control animals exhibited no differences in cardiac function at baseline compared with hour 6 (Fig. 2B). Animals in the LPS + saline group, on the other hand, exhibited significant depression in cardiac function as evidenced by a drop in EF and FS from baseline of 26% and 37%, respectively (Fig. 2C). Function in LPS + MSC-treated animals was also depressed from baseline to hour 6, but less severely compared with the LPS + saline group, with EF and FS levels declining only 10% and 17%, respectively (Fig. 2D). When compared across all groups, cardiac function at hour 6 was significantly improved in MSC-treated animals versus LPS + saline animals (Fig. 3).

Fig. 2

Fig. 2

Fig. 3

Fig. 3

Back to Top | Article Outline

Systemic cytokine levels

The levels of TNF-α, IL-1β, IL-6, and IL-10 were evaluated at the end of the experimental protocol (Fig. 4). No changes in TNF-α levels were observed between groups. Infusion of LPS resulted in significantly elevated levels of IL-1β, IL-6, and IL-10 in the vehicle-treated group. Levels of IL-1β and IL-6 in the MSC-treated group, however, were significantly reduced compared with the vehicle-treated group. On the other hand, IL-10 levels were significantly elevated in the MSC-treated group.

Fig. 4

Fig. 4

Back to Top | Article Outline

Local tissue cytokine levels

LPS injection was associated with elevated levels of TNF-α, IL-1β, and IL-6 in myocardial tissue (Fig. 5). Treatment with MSCs, however, was associated with a reduction in the levels of each of these cytokines as compared with the vehicle-treated group. No differences in IL-10 levels were detected between groups.

Fig. 5

Fig. 5

Back to Top | Article Outline

Fate of injected cells

Heart, lung, liver, spleen, and blood were analyzed for the presence of the previously injected MSCs. Cells were frequently detected in both lung and liver tissue (Fig. 6). Cells were noted only rarely in spleen tissue and were not detected in heart tissue or blood (data not shown).

Fig. 6

Fig. 6

Back to Top | Article Outline

DISCUSSION

We report the first observations that, when infused intravenously, rat bone marrow-derived MSCs are capable of altering the characteristic inflammatory response generated during endotoxemia and thereby reduce local myocardial inflammation and improve cardiac function. In general, treatment with these cells was associated with a reduction in local and systemic levels of proinflammatory cytokines, an increase in the anti-inflammatory cytokine, IL-10, and a corresponding reduction in the left ventricular dysfunction that is characteristic of endotoxemia.

The onset of sepsis and SIRS is characterized by an intense elaboration of proinflammatory cytokines such as TNF-α, IL-1β, and IL-6 by monocytes and macrophages. A compensatory release of regulatory cytokines including IL-10 occurs concomitantly with this proinflammatory cytokine surge. In many cases, this countersurge may be insufficient or even counterproductive by the time it is fully established (17). One mechanism by which stem cells may alter the inflammatory response during sepsis is via interacting with host monocytes and macrophages and "reprogramming" them, promoting an increase in IL-10 production, and a corresponding reduction in proinflammatory cytokines (8, 9, 18, 19). This has been established in previous studies in which coculture of MSCs with macrophages promotes the above cytokine production pattern in the latter (8, 9). This may also serve as a basic explanation for the reduction in serum and myocardial cytokine levels in the elevation of IL-10 in this series of experiments.

Left ventricular cardiac dysfunction during severe sepsis and SIRS is commonly observed and contributes to the prolonged and often refractory nature of the circulatory collapse associated with these conditions. The disorder occurs secondary to the direct toxic effects exerted by high levels of circulating proinflammatory cytokines such as TNF-α, IL-1β, and IL-6 on cardiomyocytes (20). These cytokines cause alterations in cardiomyocyte calcium homeostasis, pathologic upregulation of inducible nitric oxide synthase in the myocardium, subsequent generation of high loads of toxic oxygen species, and mitochondrial dysfunction resulting in a syndrome of both systolic and diastolic cardiac dysfunction (21, 22). These changes are reversed only upon recovery from the condition and, if not reversed or prevented, contribute to high rates of mortality (2).

A model of endotoxemia-induced cardiac dysfunction was used herein. Although murine endotoxemia does not sufficiently mimic the complexity of human sepsis, it produces a rapid and intense SIRS response characterized by high-circulating levels of proinflammatory cytokines that result in a reliable and measurable decrease in left ventricular cardiac function. The employment of echocardiography in such a model affords the unique opportunity to directly assess in vivo organ dysfunction similar to that which occurs during sepsis using a clinically relevant technique. A significant improvement in left ventricular cardiac function assessed by EF and FS was observed in endotoxemic animals treated with MSCs as opposed to vehicle. This represents a proof in principle of the hypothesis that the blunting of cardiotoxic systemic proinflammatory cytokine production associated with MSC administration is associated with significantly improved in vivo cardiac function during endotoxemia.

Although the precise mechanisms of the observed effect are not definitively established by these studies, evidence suggests that the improved cardiac function associated with MSC treatment occurs chiefly because of the interaction between the MSCs and cells of the innate immune system. This is supported by previous studies by our group and others that have observed a shift in the cytokine expression by sepsis or LPS-activated macrophages (8, 9). This shift includes a reduction in the secretion of proinflammatory cytokines including TNF-α, IL-1β, and IL-6, whereas a concurrent increase in IL-10 production is observed. Indeed this, in general, is consistent with both the systemic and myocardial cytokine profiles observed in this study. In addition, it is important to consider that MSCs have several other trophic and antiapoptotic characteristics such that, if they were to home to and incorporate into cardiac tissue directly, they could protect against cardiac dysfunction via several local, non-immune-mediated mechanisms including production of paracrine growth factors (23). The fact that these cells are not detected in cardiac tissue, however, is a novel finding and further makes the case that the benefits associated with MSC treatment are related to their systemic effects and not their local actions. In general, we postulate a model by which infused MSCs interact with host macrophages in circulation and tissue and reduce their expression of proinflammatory cytokines, while promoting their expression of the regulatory cytokine, IL-10. A reduction in levels of circulating proinflammatory cytokine levels, then, is responsible for the improved cardiac function that is observed following MSC treatment. On a molecular level, previous studies have suggested that this ability of MSCs to affect macrophage function may depend on their ability to respond to the septic environment via tumor necrosis factor receptors and Toll-like receptors, as well as their ability to secrete paracrine regulatory molecules such as prostaglandin E2 (8, 18).

At hour 6 of the experiment (5 h after MSC injection), MSCs were detected in parenchyma of the lung and liver. It has been previously documented that MSCs, when infused systemically in models of systemic inflammation, home to the lung in large quantities (8-10). Once in the systemic circulation, MSCs appear to follow chemotactic gradients similar to those followed by immune cells and other bone marrow progenitor cells (24). This may, in part, explain these cells' propensity to travel to lung tissue. Once there, MSCs encounter a plethora of macrophages, neutrophils, and other immune cells and, as such, have ample opportunity to exert their influence on these immune cells. The detection of MSCs in relative abundance in the liver was an unexpected finding. The reason for their presence in the liver may be related to their chemoattractant draw due to the abundance of inflammation and inflammatory cells present in the liver in addition to the extensive sinusoidal spaces and capillary networks present here, a similar situation as is encountered in the lung during endotoxemia.

Mesenchymal stem cells possess several desirable traits that could make them attractive candidates as therapeutic agents for SIRS and sepsis. They have the potential to act as a more dynamic therapy as they may interact with the dysfunctional host immune system in a multitude of ways and exert ongoing effects. This represents a change in paradigm from monoclonal antibody-based therapies targeting only one specific cytokine or molecule that have been mostly unsuccessful in the treatment of these conditions. In addition, the ability of MSCs to prevent apoptosis and promote the healing and preservation of nonimmune tissue via the elaboration of a variety of paracrine growth factors may represent another manner in which these cells could protect against the organ damage induced by sepsis (25, 26). Mesenchymal stem cells can also be easily harvested and maintained in culture, and their low rates or lack of major histocompatibility antigen and other costimulatory cell surface molecules makes these cells relatively hypoimmunogenic, thus allowing for the possibility of allogeneic, non-human leukocyte antigen-matched infusions (7).

As investigations examining the utility of MSCs in the treatment of sepsis and SIRS move forward, several areas will need to be considered. First, although studies are few in the setting of sepsis or SIRS, MSCs also exert effects on both T and B lymphocytes, neutrophils, and dendritic cells in addition to their influence on macrophages (27). Although some of these interactions may offer potential benefit in the setting of sepsis, it is possible that some may also produce detrimental results. For example, MSCs can promote an increase in the relative proportion of CD4+ T helper 2 (TH2) lymphocytes and CD4+ regulatory T lymphocytes to CD8+ cytotoxic T lymphocytes. The net result appears to be a reduction in T-cell-mediated immunity with an increase in IL-4 production by CD4+ TH2 lymphocytes and a reduction in interferon γ production by CD8+ T lymphocytes (28, 29). Although the effect of MSCs on T-cell function during sepsis and SIRS has not yet been studied specifically, the above findings may cause legitimate concern that these cells could exacerbate the already present deficiencies in T-cell-mediated immunity that is increasingly being recognized as an important contributor of the pathogenesis of sepsis and the ensuing multiorgan dysfunction (30, 31). Future studies will need to address how MSCs' influence on other immune cell types may render them as beneficial or detrimental in the setting of systemic inflammation and/or infection. Furthermore, although endotoxemia offers a valuable tool to study cardiac dysfunction that is similar to that observed in sepsis, future efforts that seek to further delineate the complex effects of MSCs on the host immune system during sepsis should use polymicrobial models such as cecal ligation and puncture to better mimic the complex and ongoing immune response that characterizes human sepsis (32). As these cells have already been shown to confer a survival advantage in this model, further investigation into their use for the treatment of sepsis is warranted. Variations in the timing and dosage of MSC administration must be investigated, as should variations in the severity and duration of sepsis. The fate of these cells should also be assessed over longer periods to assess their true survival and whether their impact may wane or change with time and/or whether repeat dosing may be of utility.

Back to Top | Article Outline

REFERENCES

1. Fernandes CJ Jr, Akamine N, Knobel E: Myocardial depression in sepsis. Shock 30(Suppl 1):14-17, 2008.
2. Zanotti-Cavazzoni SL, Hollenberg SM: Cardiac dysfunction in severe sepsis and septic shock. Curr Opin Crit Care 15:392-397, 2009.
3. Levy RJ: Mitochondrial dysfunction, bioenergetic impairment, and metabolic down-regulation in sepsis. Shock 28:24-28, 2007.
4. Parrillo JE, Burch C, Shelhamer JH, Parker MM, Natanson C, Schuette W: A circulating myocardial depressant substance in humans with septic shock. Septic shock patients with a reduced ejection fraction have a circulating factor that depresses in vitro myocardial cell performance. J Clin Invest 76:1539-1553, 1985.
5. Meldrum DR: Tumor necrosis factor in the heart. Am J Physiol 274:R577-R595, 1998.
6. Meng X, Ao L, Meldrum DR, Cain BS, Shames BD, Selzman CH, Banerjee A, Harken AH: TNF-alpha and myocardial depression in endotoxemic rats: temporal discordance of an obligatory relationship. Am J Physiol 275:R502-R508, 1998.
7. Nauta AJ, Fibbe WE: Immunomodulatory properties of mesenchymal stromal cells. Blood 110:3499-3506, 2007.
8. Nemeth K, Leelahavanichkul A, Yuen PS, Mayer B, Parmelee A, Doi K, Robey PG, Leelahavanichkul K, Koller BH, Brown JM, et al.: Bone marrow stromal cells attenuate sepsis via prostaglandin E(2)-dependent reprogramming of host macrophages to increase their interleukin-10 production. Nat Med 15:42-49, 2009.
9. Weil BR, Herrmann JL, Abarbanell AM, Manukyan MC, Poynter JA, Meldrum DR: Mesenchymal stem cells attenuate myocardial functional depression and reduce systemic and myocardial inflammation during endotoxemia. Surgery 148:444-452, 2010.
10. Xu J, Woods CR, Mora AL, Joodi R, Brigham KL, Iyer S, Rojas M: Prevention of endotoxin-induced systemic response by bone marrow-derived mesenchymal stem cells in mice. Am J Physiol Lung Cell Mol Physiol 293:L131-L141, 2007.
11. Gupta N, Su X, Popov B, Lee JW, Serikov V, Matthay MA: Intrapulmonary delivery of bone marrow-derived mesenchymal stem cells improves survival and attenuates endotoxin-induced acute lung injury in mice. J Immunol 179:1855-1863, 2007.
12. Gonzalez-Rey E, Anderson P, Gonzalez MA, Rico L, Buscher D, Delgado M: Human adult stem cells derived from adipose tissue protect against experimental colitis and sepsis. Gut 58:929-939, 2009.
13. Lee JW, Fang X, Gupta N, Serikov V, Matthay MA: Allogeneic human mesenchymal stem cells for treatment of E. coli endotoxin-induced acute lung injury in the ex vivo perfused human lung. Proc Natl Acad Sci U S A 106:16357-16362, 2009.
14. Weil BR, Markel TA, Herrmann JL, Abarbanell AM, Kelly ML, Meldrum DR: Stem cells in sepsis. Ann Surg 250:19-27, 2009.
15. Sun S, Guo Z, Xiao X, Liu B, Liu X, Tang PH, Mao N: Isolation of mouse marrow mesenchymal progenitors by a novel and reliable method. Stem Cells 21:527-535, 2003.
16. Abarbanell AM, Wang Y, Herrmann JL, Weil BR, Poynter JA, Manukyan MC, Meldrum DR: Toll-like receptor 2 mediates mesenchymal stem cell-associated myocardial recovery and VEGF production following acute ischemia-reperfusion injury. Am J Physiol Heart Circ Physiol 298:H1529-H1536, 2010.
17. Reim D, Westenfelder K, Kaiser-Moore S, Schlautkotter S, Holzmann B, Weighardt H: Role of T cells for cytokine production and outcome in a model of acute septic peritonitis. Shock 31:245-250, 2009.
18. Spaggiari GM, Abdelrazik H, Becchetti F, Moretta L: MSCs inhibit monocyte-derived DC maturation and function by selectively interfering with the generation of immature DCs: central role of MSC-derived prostaglandin E2. Blood 113:6576-6583, 2009.
19. Kim J, Hematti P: Mesenchymal stem cell-educated macrophages: a novel type of alternatively activated macrophages. Exp Hematol 37:1445-1453, 2009.
20. Maass DL, White J, Horton JW: IL-1beta and IL-6 act synergistically with TNF-alpha to alter cardiac contractile function after burn trauma. Shock 18:360-366, 2002.
21. Sharma AC: Sepsis-induced myocardial dysfunction. Shock 28:265-269, 2007.
22. Rossi MA, Celes MR, Prado CM, Saggioro FP: Myocardial structural changes in long-term human severe sepsis/septic shock may be responsible for cardiac dysfunction. Shock 27:10-18, 2007.
23. Crisostomo PR, Wang M, Markel TA, Lahm T, Abarbanell AM, Herrmann JL, Meldrum DR: Stem cell mechanisms and paracrine effects: potential in cardiac surgery. Shock 28:375-383, 2007.
24. Chamberlain G, Fox J, Ashton B, Middleton J: Concise review: mesenchymal stem cells: their phenotype, differentiation capacity, immunological features, and potential for homing. Stem Cells 25:2739-2749, 2007.
25. Crisostomo PR, Wang Y, Markel TA, Wang M, Lahm T, Meldrum DR: Human mesenchymal stem cells stimulated by TNF-{alpha}, LPS, or hypoxia produce growth factors by an NF{kappa}B- but not JNK-dependent mechanism. Am J Physiol Cell Physiol 294:C675-C682, 2008.
26. Wang M, Crisostomo PR, Herring C, Meldrum KK, Meldrum DR: Human progenitor cells from bone marrow or adipose tissue produce VEGF, HGF, and IGF-I in response to TNF by a p38 MAPK-dependent mechanism. Am J Physiol Regul Integr Comp Physiol 291:R880-R884, 2006.
27. Rasmusson I: Immune modulation by mesenchymal stem cells. Exp Cell Res 312:2169-2179, 2006.
28. Zappia E, Casazza S, Pedemonte E, Benvenuto F, Bonanni I, Gerdoni E, Giunti D, Ceravolo A, Cazzanti F, Frassoni F, et al.: Mesenchymal stem cells ameliorate experimental autoimmune encephalomyelitis inducing T-cell anergy. Blood 106:1755-1761, 2005.
29. Aggarwal S, Pittenger MF: Human mesenchymal stem cells modulate allogeneic immune cell responses. Blood 105:1815-1822, 2005.
30. Unsinger J, Kazama H, McDonough JS, Griffith TS, Hotchkiss RS, Ferguson TA: Sepsis-induced apoptosis leads to active suppression of delayed-type hypersensitivity by CD8+ regulatory T cells through a TRAIL-dependent mechanism. J Immunol 184:6766-6772, 2010.
31. Brahmamdam P, Watanabe E, Unsinger J, Chang KC, Schierding W, Hoekzema AS, Zhou TT, McDonough JS, Holemon H, Heidel JD, et al.: Targeted delivery of siRNA to cell death proteins in sepsis. Shock 32:131-139, 2009.
32. Hubbard WJ, Choudhry M, Schwacha MG, Kerby JD, Rue LW 3rd, Bland KI, Chaudry IH: Cecal ligation and puncture. Shock 24(Suppl 1):52-57, 2005.
Keywords:

Sepsis; inflammation; tumor necrosis factor; progenitor cells; echocardiography; myocardial dysfunction; immunomodulation

©2011The Shock Society